Oxidative stress generated by exercising humans and the potential for attenuating its damage by antioxidants is the basis for this proposal. The investigators have demonstrated previously that endurance exercise causes an increase in lipid peroxidation in apparently well nourished athletes. Therefore, they plan to use the same exercise protocol, a 50 km ultramarathon run as the model system with the exception that runners will be supplemented with antioxidants or placebo. The hypothesis to be tested is that the oxidative stress generated during endurance exercise can be inhibited by antioxidant supplementation. Specifically, supplementation with vitamin E and/or vitamin C, which are known to inhibit lipid peroxidation, could be beneficial in preventing such damage. Specific Aim. Can the oxidative stress of endurance exercise be alleviated by prior antioxidant supplementation? Thirty-two subjects (16 females, 16 males) will be studied during a 50 km (30 mile) ultramarathon. Subjects will be randomly assigned to one of four study groups: (1) placebos, (2) 1000 mg vitamin C (500 mg twice a day), (3) 400 IU vitamin E (RRR-alpha-tocopheryl acetate), or (4) both 1000 mg vitamin C and 400 IU vitamin E. Subjects will consume a prescribed diet daily for 6 weeks prior to the race, race day and throughout the blood drawing schedule. Subjects will consume a prescribed diet daily for 6 weeks prior to the race, and then a controlled diet the day prior to the race, subjects will consume deuterium-labeled vitamin E (75 mg d6RRR-alpha-tocopheryl acetate) that will act as a tracer for vitamin E turnover during the race. Blood samples will be obtained up to 3 days after the race for measurements of d6-alpha-tocopherol, markers of lipid peroxidation and markers of inflammation. Deuterated tocopherol disappearance rates and areas under the curve (AUC) will be calculated. Lipid peroxidation markers (plasma F2-isoprostanes), low density lipoprotein (LDL) oxidation kinetics, and markers of inflammation will all be measured. The proposed study will evaluate whether supplementation with vitamin E and/or C can decrease the levels of F2-isoprostanes generated during endurance exercise and whether they can reduce the rate at which deuterated vitamin E disappears. Finally, the investigators plan to measure markers of inflammatory response, such as C-oxidants increase and vitamin E decreases these markers.